Field of the Invention
The present invention relates to a hybrid drive device to which an engine and a motor-generator are provided as sources of drive power.
Description of the Related Art
In a hybrid drive device, a system is per se known in which a dog clutch DC3 and a one-way clutch OC3 are provided between a rotor shaft of a first motor-generator MG1 and a case C of a hybrid transaxle, and in which one engagement member of the dog clutch DC3 is connected to the one-way clutch OC3 while the other engagement member of the dog clutch DC3 is fixed to the case C (see Japanese Patent Application Publication No. 2010-36880 (JP-A-2010-36880)). With this type of hybrid drive device, by controlling the dog clutch DC3 to be in its engaged state during high speed traveling, a state is established in which, due to the one-way clutch OC3, positive rotation of the first motor-generator MG1 is prevented while negative rotation of the first motor-generator MG1 is permitted. Since, due to this, a Hi gear locked mode which is a parallel mode to the high speed sift position (Hi) is implemented, accordingly it is possible to enhance the energy efficiency during high speed traveling.
And now, a selectable one-way clutch is per se known that is capable of selecting either a locked mode in which, during rotation, it permits torque transmission between two members only in a predetermined single rotational direction, or a free mode in which, during rotation, it separates torque transmission in both directions between those two members. Since such a selectable one-way clutch is endowed with this type of function, accordingly it is possible to replace the dog clutch DC3 and the one-way clutch OC3 of the above described hybrid drive device of JP-A-2010-36880 with this selectable one-way clutch, which is a unitary device. In detail, it is possible to make such a selectable one-way clutch function in a similar manner to the hybrid drive device of JP-A-2010-36880 by fixing one of its two members to the case C, which thus serves as a fixed member, while connecting the other of the two members to the rotor shaft of the first motor-generator MG1, which thus serves as a rotating member.
In a hybrid drive device in which the replacement described above has been performed, the rotating member of the selectable one-way clutch receives and bears the reaction torque of the engine torque outputted by the engine. In the state in which engine combustion is stable, the engine torque continues to be outputted in the positive direction. Due to this, during the locked mode in the state in which positive rotation of the rotating member is prevented, the state in which torque acts in the positive direction upon the rotating member continues. Accordingly, in the state in which combustion in the engine remains stable, in the locked mode, the engagement of the selectable one-way clutch is maintained.
However if, in the locked mode, an engine combustion anomaly occurs and leads to reduction of the engine torque, then the engine rotational speed decreases. Together with this decrease, the torque upon the rotating member whose positive rotation was prevented is removed, so that the engagement is temporarily released and negative rotation occurs. When thereafter the engine combustion returns to normal, the engine rotational speed rises. Due to this, there is a possibility that the components of the selectable one-way clutch may be damaged when its re-engagement occurs. Moreover, there is a possibility that wear or strange noises may be generated due to the occurrence of ratcheting, which is a phenomenon in which, in a situation in which the engine torque is great during the above return to normal, the rotating member rotates in the positive rotational direction, which is the direction in which it is not properly supposed to rotate.
Accordingly, an object of the present invention is to provide a hybrid drive device which, when an engine combustion anomaly occurs, is capable of avoiding deterioration of components of a selectable one-way clutch and the generation of wear or strange noises due to the occurrence of ratcheting.